WO 2008/075268 A1 does disclose a direct digital receiver for an RF coil, in particular of a magnetic resonance imaging system. To obtain that the sampling frequency of an analogue-to-digital converter of the digital receiver can be chosen independently of the digital operating frequency at which the subsequent digital down converter operates, a resampling unit is introduced which is coupled between said analogue-to-digital converter and said digital down converter.
However, the resampling DDR still requires the ADC sampling frequency to remain in frequency lock with the system clock used to control the time critical digital functions of the system.
Frequency lock on the ADC clock has two disadvantages: First, it requires a system clock to be distributed to the ADC. This limit is restricting the ADC and associated clock to locations where the system clock is present. Second, the derivation of an ADC sampling frequency from the recovered system clock inherently introduces noise present on the system clock into the ADC clock. The fidelity of the system clock is difficult to maintain as it is typically traversing various digital electronic assemblies.